Streamflow Response to Climate:
Why Geology Matters
– Tim Mayer, US Fish and Wildlife Service
Presented at the
Oregon Water Conference
Corvallis, OR
May 24-25, 2011
Warmer temperatures, reduced snowpacks,
earlier snowmelt and more winter rain v snow
will lead to:
Earlier timing of snowmelt runoff
Decreased summer/fall baseflows
Increased water temperatures
Increased winter flooding
Purpose of Study
To consider how climate change impacts to streams
vary for different stream types, as defined by
elevation and geology.
Focus on the Pacific Northwest.
Olympic Nat Park
Crater Lake Nat Park
Mt Rainier Nat Park
Surface-dominated and Groundwater-dominated
Flow Regimes
Mean Daily Discharge 1960-1989 for Three Stream Types
Rain Basin, Snowmelt Basin, and Groundwater Basin
Discharge (mm/day)
10
8
6
4
2
Little R (rain)
Salmon R (snowmelt)
McCloud R (groundwater)
0
Oct
River
Dec
Feb
Type
Little R, OR
Surface Rain
Salmon R, CA Surface Snowmelt
McCloud R, CA Groundwater
Apr
Elev
(m)
860
1300
1500
Jun
Annual Pcp
(cm/yr)
156
141
143
Aug
Oct
Annual Runoff
(cm/yr)
89
83
87
USGS Grid Map of Baseflow Index (Wolock, 2003)
Stream Types and Summer Streamflow
Contrast in summer flows in two Oregon rivers
Groundwater-dominated
stream
Surface-dominated stream
Importance of Groundwater Basins (sub-watersheds)
to Mainstem Flows on Three Major River Systems
Average Monthly Flow Upstream as a % of Downstream Flow
for the Klamath R, the Umpqua R, and the Rogue R
100
Flow %
80
60
Klamath
Umpqua
Rogue
40
20
0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Predicted v Observed Low Flow (P10) for 281 OR Streams
Multiple Linear Regression
Predictors: Drainage area, Pcp, Longitude, (BFI)
no BFI
r2 = 0.56
Predicted Log P10
4
3
2
1
0
-1
-2
-2
-1
0
1
2
3
4
-2
-1
0
1
2
3
4
w/ BFI
r2 = 0.86
Predicted Log P10
4
3
2
1
0
-1
-2
Observed Log P10
Stream Types and Climate Change Impacts
Earlier timing of snowmelt runoff
and decreased baseflows
Mayer and Naman (2011) compared trends in monthly
and annual streamflows from 1956 to 2005 among
stream types.
 Examined 10 rain basins, 5 snowmelt basins, and
11 groundwater basins (all with minimal regulation
and diversion).
 Rain Basins – large and variable trends in
monthly flows in winter, very small trends in
summer.
10 Surface-dominated Rain Basins
Change in Flow
(mm/day)
2
1
0
-1
-2
-3
Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
WY
Mayer and Naman (2011)
 Snowmelt Basins – little or no change in monthly
flows in winter, increases in early spring,
decreases in late spring, very small trends in
summer.
Change in Flow
(mm/day)
2
5 Surface-dominated Snowmelt Basins
1
0
-1
-2
-3
Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
WY
Mayer and Naman (2011)
 Groundwater Basins – more uniform trends
(mostly declines) in all months, less of a decline or
even increases at some sites in Mar/ Apr, relatively
large declines in summer/fall flows in comparison
to surface-dominated streams.
11 Groundwater-dominated Basins
Change in Flow
(mm/day)
2
1
0
-1
-2
-3
Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
WY
Mayer and Naman (2011)
“…absolute decreases in July-September baseflows
are significantly greater, by an order of magnitude, in
groundwater basins compared to surface-dominated
basins…”
Mayer and Naman (2011)
Stream Types and Climate Change Impacts
Warmer Water Temperatures?
Groundwater-dominated
stream
Surface-dominated stream
Stream/Air Temperature Relationship
Relationship of Stream/Air Temperature
Williamson River and Sprague River, OR 2007-2010
Weekly 7D Avg Stream T (C)
25
Sprague R nr Chiloquin, OR
BFI=0.79
20
15
10
5
0
-5
Williamson R blw Sprague nr Chiloquin, OR
BFI=0.90
-10
-10
-5
0
5
10
15
20
Weekly 7D Avg Air T Agency Lake, OR (C)
25
Summer Stream/Air Temperature Relationship
Relationship of Jul-Aug Stream/Air Temperature
Williamson River and Sprague River, OR 2007-2010
Weekly 7D Avg Stream T (C)
28
Sprague R nr Chiloquin, OR
BFI = 0.79
24
y = 0.61x + 10.8
20
16
y = 0.39x + 7.94
12
Williamson R blw Sprague nr Chiloquin, OR
BFI = 0.90
8
8
12
16
20
24
Weekly 7D Avg Air T Agency Lake, OR (C)
28
7 Stream Temperature Sites
In the North Umpqua and Upper Rogue
August Stream/Air Temperature Relationships
August Stream/Air Temperature Relationship
7 Stream Sites in the Umpqua and Rogue
Aug Weekly 7-D Average Stream T (C)
30
25
20
15
10
5
5
10
15
20
Aug Weekly 7-D Average Air T (C)
25
30
August Stream/Air Temperature Relationships
August Stream/Air Temperature Relationship
7 Stream Sites in the Umpqua and Rogue
Aug Weekly 7-D Average Stream T (C)
30
25
BFI = 0.42
BFI = 0.45
20
BFI = 0.53
BFI = 0.66
BFI = 0.68
15
BFI = 0.81
BFI = 0.88
10
5
5
10
15
20
Aug Weekly 7-D Average Air T (C)
25
30
Regression Results from August Stream/Air
Temperature Relationships
Aug 7-D Avg Stream T/Air T v BFI
7 Stream Sites in the Rogue/Umpqua
Ratio of Aug 7-D Stream T/Air T
1.4
1.2
1.0
0.8
0.6
y = -1.01x + 1.43
r2 = 0.96
0.4
0.2
0.0
0.0
0.2
0.4
0.6
BFI
0.8
1.0
Regression Results from August Stream/Air
Temperature Relationships
Aug 7-D Avg Stream T/Air T v BFI
14 Stream Sites in OR
Ratio of Aug 7-D Stream T/Air T
1.4
1.2
1.0
0.8
0.6
0.4
Umpqua/Rogue sites
Other Misc OR sites
0.2
0.0
0.0
0.2
0.4
0.6
BFI
0.8
1.0
Regression Results from August Stream/Air
Temperature Relationships
Slope of Linear Regression of Aug Stream to Air Temp
7 Stream Sites in the Rogue/Umpqua
1.0
Air Temp Coefficient
0.8
0.6
0.4
y = -0.58x + 0.80
r2 = 0.78
0.2
0.0
0.0
0.2
0.4
0.6
BFI
0.8
1.0
Regression Results from August Stream/Air
Temperature Relationships
Slope of Linear Regression of Aug Stream to Air Temp
14 Stream Sites in OR
1.0
Air Temp Coefficient
0.8
0.6
0.4
0.2
0.0
0.0
0.2
0.4
0.6
BFI
0.8
1.0
Potential Climate Change Impacts to
Groundwater-dominated Streams
 Changes in timing and baseflows
– Groundwater basins show some indication of earlier timing
of snowmelt runoff due to reduced snowpack but timing
changes are more subtle and spread out. The effects of
reduced snowpacks are extended into summer, resulting
in larger absolute decreases in summer baseflows.
Potential Climate Change Impacts to
Groundwater-dominated Streams
 Warmer water temperatures
– Summer water temperatures are considerably cooler in
groundwater-dominated streams and these systems may
be less sensitive to increasing summer air temperatures
than surface-dominated streams.
Questions?
Olympic Nat Park
Mt Rainier Nat Park
Crater Lake Nat Park